What can we do to restart fermentation that got stuck over the winter?

Our club brewed about 7 gallons of this recipe in November. Primary went well, but then the weather got cold and the yeast went dormant, leaving the gravity at ~1.045. We left it until the weather got warmer this spring. When it didn't come back on it's own, we pitched several packets of dry champagne yeast. The first packet didn't seem to do anything, so we moved it to an even warmer (75ish deg) room and pitched more yeast. It's now bubbling slowly, but has only come down in gravity to 1.040 in the past week. Are there any additional things we could try to get it going again?

3 Answers
3

Pitching yeast directly into wort is not a good idea - it reduces the viability by at least half for normal strength wort, and presumably even more for higher gravity or higher alcohol worts.

You have a lot of yeast in this brew, presumably dead or dying, so I would consider racking soon to avoid picking up a yeast bite in the beer. A schedule like this should help

make a big starter - pitch some fresh yeast, ideally the same strain from the recipe into fresh wort. 2 liters would be the minimum. If the yeast is dry, be sure to rehydrate according to the packet instructions - this is key to obtaining the highest viability. If you have a stirplate, use that also.

When the yeast are actively fermenting, typicaly after 24-36 hours, rack your partially fermented wort to a new vessel, to get it off all the existing, mostly dead yeast, and pitch the actively fermenting starter.

The actively fermenting yeast should have a high alcohol tolerance, ideally the abbey yeast from the recipe, to preserve the intended characteristics of the brew. I don't recommend champagne yeast, unless you are sure the remaining wort contains little maltose.

Something to consider is to incrementally add wort from your brew to the starter while it's fermenting to get the yeast gradually acclimatized to the alcohol.

So, in short, rack the beer off the old yeast, and pitch actively fermenting yeast. That should get it started.

Given the amount of extract you used, you might not have a stuck fermentation. It might very well be done. You don't know how the extract was made and between the mash temp used and additional unfermentable ingredients in the extract it can leave you with a a high FG. More sugar would have helped, but at this point I think your choices are to either drink it as is or blend it with another beer.

RDWHAHB. It takes a while and it might actually dry-out more than you expect. This is based on personal experience.

I had a very similar situation myself. OG 1.101 stalled at 1.033. I rehydrated champaign yeast, pitched, and moved the carboy to a 70F to 74F degree environment (from the 62F range). Final gravity was actually a bit lower than I wanted (1.018), but it took a while.